JEE Main 2021 · ChemistryNumerical answerNumerical valueEasyCalculation

JEE Main 27 August 2021, Shift 2, Chemistry Q53

Question 53 of 90 in this shift, Chemistry question 23 of 30, Section B.

The number of photons emitted by a monochromatic (single frequency) infrared range finder of power 1 mW and wavelength of 1000 nm, in 0.1 second is

x \times 10^{13}

. The value of

x

is __________. (Nearest integer) (h =

6.63 \times 10^{-34}

Js, c =

3.00 \times 10^{8}

\mathrm{ms^{-1}}

)

Official answer

NTA final key.

Chapter: Structure of Atom
Topic: Photoelectric Effect
Idea tested: Photon Energy and Momentum

Same idea in other shifts

Asked 5× in all

8 Apr 2026, Shift 2 · Q38A monochromatic source of light operating at 15 kW emits $2.5 \times 10^{22}$ photons/s. The region of an electromagnetic spectrum to…MediumSingle correct
2 Apr 2025, Shift 1 · Q44A monochromatic light is incident on a metallic plate having work function $\phi$ . An electron, emitted normally to the plate from a point…MediumSingle correct
13 Apr 2023, Shift 2 · Q60An atom absorbs a photon of wavelength $500$ nm and emits another photon of wavelength $600$ nm. The net energy absorbed by the atom in…MediumNumerical value
24 Feb 2021, Shift 1 · Q18Given below are two statements : Statement I : Two photons having equal linear momenta have equal wavelengths. Statement II : If the…EasyTwo statements

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.